The overall goal of this project is to develop new modalities of functional imaging in living tissues. To reach this goal we will use a new concept of Variable Field (VF) and Variable Radio Frequency (VRF) proton electron double resonance imaging (PEDRI) in combination with design of specific paramagnetic probes. This will allow for functional mapping using (e.g. oxygen or pH mapping) within MRI high quality spatial resolution and short acquisition time. The specific aims are: (SA1) To develop Variable Field PEDRI for functional imaging of paramagnetic probes. The approach will allow for pH mapping using available probes, screening newly synthesized probes, and optimization of VRF PEDRI spectroscopic parameters for functional pH and oxygen mapping. (SA2) To develop PEDRI-oriented functional probes: nitroxyl and trityl radicals. Nitroxide probes with enhanced stability towards reduction, and dual function pH- and oxygen triarylmethyl probes will be synthesized and used for VF/VRF PEDRI. Synthesis an optimization of the probes is absolutely crucial for the overall efficiency of functional PEDRI applications. (SA3) To develop Variable Radio Frequency PEDRI for functional mapping of living tissues. VRF PEDRI is an instrumentally innovative modification of PEDRI approach. Compared with VF PEDRI this approach will use stationary magnetic field but slightly different EPR RF excitation frequencies resulting improved magnetic field homogeneity and stability, and decreased acquisition time. It will also provide opportunity for future development of a simplified PEDRI system based on conventional NMR gradients. The capacity of the functional PEDRI for in vivo pH and oxygen mapping will be demonstrated for the most effective probes in PyMT mammary tumors of FVB/N female mice. In a tumor microenvironment, both oxygen and pH changes are indicative of tumor progression being important factors for prognosis and treatment. In summary, the success of this project may have a significant impact on the future of in vivo functional imaging applications to medicine. PUBLIC HEALTH RELEVANCE: This project will develop new modalities of functional mapping of living tissues based on MRI of specific paramagnetic probes. Application experiments will use newly designed probes for pH- and oxygen mapping of mammary tumors in living mice. The developed technique may have a significant impact on the future applications to medical imaging.